Until recently, scientists did not know of a close verte- brate analogue to the extreme form of altruism abserved in eusocial insects like ants and bees, whereby individuals cooperate, sometimes even sacrificing their own oppor- ( 5) tunities to survive and reproduce, for the good of others. However, such a vertebrate society may exist among under- ground colonies of the highly social rodent Heterocephalus glaber, the naked mole rat.